To control the flow; should I put a ball valve before the IN or after the OUT.... My march also came with a filter housing and some filters, anyone filtering their wort from the BK before they hit the fermenter or are you supposed to filter after fermentation (I keg so I don't care about the yeasties)

Yeah, there is no point in filtering prior to the ferment, as you are introducing yeast anyway. Also, if you filter out all of the trub, you will impede the health of your yeast, as trub has been found to be GOOD for yeasties.